1. Field of the Invention
Embodiments of the present invention relate to a rechargeable battery having an improved safety device.
2. Description of the Related Art
Unlike a primary battery, a rechargeable battery may be charged and discharged over and over again. A low capacity secondary battery that comprises a pack shaped battery cell may be used as a power source for various small portable electronic devices such as cellular phones, and camcorders. A high capacity secondary battery that has several tens of the battery cells that are connected may be used as a power source for driving motors such as in a hybrid automobile.
The rechargeable battery may be fabricated into various shapes, including a cylindrical and a prismatic shape, and may comprise an electrode assembly comprising an insulating separator interposed between a positive electrode and a negative electrode, the resultant being wound and inserted into a case. The case is closed and sealed with a cap assembly having an outer terminal to provide a battery.
Meanwhile, a rechargeable battery has a great potential for fire or explosion due to an increased internal pressure when excessive heat is generated or when an electrolyte is decomposed. Accordingly, there is a need for a rechargeable battery capable of improving safety. However, I have found that earlier safety device add significantly to the volume of the rechargeable battery. Furthermore, earlier safety devices are prone to being damaged by moisture over time. Therefore, what is needed is an improved safety device that does not add to the volume of the battery and is not prone to damage due to moisture.